U.S. Pat. No. 5,258,158 (Inventor: Dray; Published: 1993 Nov. 2) discloses a valve for an injection-molding screw, and the valve includes a differential piston, which closes a material flow path prior to injection of a molding material.
U.S. Pat. No. 5,044,926 (Inventor: Dinerman et al; Published: 1991 Sep. 3) discloses a valve for an injection-molding machine. The valve has a rod for rotation and axial translation relative to an injection screw, with a retaining sleeve that limits axial movement of the rod.
U.S. Pat. No. 4,512,733 (Inventor: Eichlseder et al; Published: 1985 Apr. 23) discloses a valve for an extruder, with movement readily changed by a retracting-screw withdrawing pin and a replacing metering unit.
U.S. Pat. No. 4,062,479 (Inventor: Szabo; Published: 1977 Dec. 13) discloses a valve for a reciprocating screw-injection machine, the valves has a valve seat with an annular closure for effecting protuberance.